In recent years, the relationship of biodiversity to ecosystem stability, productivity and other ecosystem functions have been researched by using theoretical approaches, experimental investigations and observations in natural ecosystems,however, results have been controversial. For example, simple systems were more stable than complex systems in theoretical studies, higher productivity was observed in man-made ecosystems with poorer species composition than in natural ecosystems with more diverse assemblages, etc. The role of biodiversity in ecosystem functioning, such as its influence on sustainability, stability, and productivity, still is not understood. Because accelerated soil erosion in various ecosystems has caused a decrease in ecosystem primary productivity, a logical way to study the relationship between biodiversity and ecosystem function will be to study the relationship between plant species diversity and soil conservation. In addition, biodiversity is a product of evolutionary history and soil erosion is a key factor controlling the evolution of the modern environment on the surface of the Earth. A study on the relationships between biodiversity and soil erosion processes could help to understand the environmental evolution of Earth and predict the future changes.

To test this, fifteen 10 m×40 m standard runoff plots were established to measure surface runoff, soil erosion and total P leaching in different secondary communities of semi-humid evergreen broad-leaved forests that varied in composition, diversity and level of disturbance and soil erosion. The following five communities were studied: AEI (Ass.Elsholtzia fruticosa+Imperata cylindrical), APMO (Ass. Pinus yunnanensis+Myrsine africana+Oplismenus compsitus), APLO (Ass.Pinus yunnanensis+Lithocarpus dealbatus+Oplismenus compsitus), AEME (Ass. Eucalyptus smith+Myrsine africana+Eupatorium enophorum) and ACKV (Ass. Cyclobalanopsis glaucoides+Keteleeria evelyniana+Viola duelouxii) in central Yunnan Province of China (101°28'18″ E, 25°24'09″ N, 1 950-2 015 m). Tree density, the diameter of trees at breast height and the hygroscopic volume of plant leaves were determined in each plot in order to analyze the relationship between plant species diversity and ecosystem function related to soil conservation and community structure. The degraded AEI, APMO, APLO and ACKV communities were restored naturally and the AEME was restored using plantation trees ofE. smith and E. maidenii at AEI. The sequence of the successional phases were: 1) AEI AEME ACKV; 2) AEI APMO APLO ACKV. The slope degree, slope position and soil types of all plots were similar so that the results of these plots could be compared based on differences in diversity and composition only.

The results indicated that surface runoff, soil erosion and total P leaching decreased according to a power function as plant species diversity increased and the three year average was 960.20 m³·hm^-2·a^-1, 11.4 t·hm^-2·a^-1, 127.69 kg·hm^-2·a^-1 in the plot with the lowest species diversity and 75.55 m³·hm^-2·a^-1, 0.28 t·hm^-2·a^-1, 4.71 kg·hm^-2·a^-1 in the plot with the highest species diversity. The low species plot was 12, 50 and 25 times, respectively, higher than in the high species plot. Soil conservation was enhanced with increasing plant species diversity. The coefficient of variation of surface runoff, soil erosion and total P leaching also followed a power function decreasing with increasing plant species diversity from 2001 to 2003. The coefficient of variation was 287.6, 534.21, 315.47, respectively, in the lowest species diversity plot and 57.93, 187.94 and 59.2 in the highest species diversity plot, which was 4, 3 and 5 times greater in the lowest species plot. Enhanced soil conservation maintained greater stability with increased plant species diversity. Plant individual density increased linearly and the degree of closeness and basic coverage increased logarithmically with increasing plant species diversity. The hydrological function of the leaves of the plant communities was strongest in ACKV, poorest in APMO, and intermediate in the AEME, APLO and AEI communities. The hydrological function of the leaves was enhanced as the plant species diversity increased. There were obviously relationships between plant species diversity with rainfall interception, coverage, plant individual density and they were related to soil conservation once more in the five successional forest communities.

The complex relationships of plant species diversity with above-mentioned ecological processes indicated that plant species diversity was an important factor influencing the interception of rainfall reducing soil erosion and enhancing the stability of soil conservation, but the causal mechanism is not known. This experiment showed that plant species diversity promoted soil and nutrient conservation and was able to predict primary productivity of the ecosystem, and was thus a good way to study the relationship between biodiversity and ecosystem stability. Rainfall interception could be assessed easily using the hygroscopic volume of plant leaves of the plant community. Because there were strong correlations between plant species diversity and ecosystem functioning as related to soil conservation, the patterns of plant species diversity will show a certain level of predictability on the interactions of life systems with surface processes of the Earth.

The stability of ecosystems determines whether they can sustainably provide key functions and services in the background of global changes. Ecosystem stability, particularly its relation with biodiversity, is one of the central issues in ecology. Whether biodiversity enhances or impairs ecosystem stability has historically aroused much debate. Based on early reviews and studies on different aspects of stability, here we summarized recent advances from three aspects. Firstly, several recent theoretical studies offered novel insights in understanding the multi- dimensionality of stability and the intrinsic link between different stability measures, and we provided an overview on these new insights. Secondly, we reviewed recent empirical and theoretical studies on biodiversity- stability relationships, including those in the context of multidimensional stability. Thirdly, we introduced the recently developed multi-scale stability framework, which provides new opportunity to understand the scaling of stability and extend diversity-stability relations to a multi-scale context. We ended with a discussion on future research questions and directions.

Samara (winged fruit) can be dispersed easily by wind and may be a crucial factor for angiosperm spread and diversification. In a narrow sense, a samara is an indehiscent dry fruit with wing(s) developed from fruit pericarp, while in a broad sense samaras also include all winged fruits with wings developed from both pericarp and perianth or bracts. According to the wing shape and growth patterns of samaras, we divided samaras into six types, i.e. single-winged, lanceolate-winged, rib-winged, sepal-winged, bract-winged, and perigynous samaras. Perigynous samaras can be further classified into two forms, i.e. round-winged and butterfly-winged samaras. Accordingly, the aerodynamic behavior of samaras can be classified into five types, autogyro, rolling autogyro, undulator, helicopter, and tumbler. The rib-winged and round-winged samaras can be found in Laurales, a basal angiosperm, and may represent the primitive type of early samaras. In the derived clades, samaras evolved enlarged but unequal wings and decreased wing loading (the ratio of fruit weight to wing size), which is likely an adaptation to gentle wind and secondary dispersal through water or ground wind. The wings of some samaras (such as sepal-winged and bract-winged samaras) may have multiple functions including wind dispersal, physical defense for the seeds, and adjust seed germination strategy. The pantropical family Malpighiaceae is extraordinarily rich in samara types, which is likely related to its multiple inter-continent dispersal in history, which is known as “Malpighiaceae Route”. Therefore, Malpighiaceae can be used as a model system for the studies on samara adaptation and evolution. We identified the following issues that deserve further examination in future studies using both ecological and evo-devo methods: 1) the adaption of different types of samaras in dispersal processes, 2) the molecular and developmental mechanism of sepal- and bract-wings, and 3) the evolution of samara types and their effects on angiosperm diversification.

Aims Beta diversity is the variation in species composition among sites in a geographic region. Beta diversity is a key concept for understanding the functioning of ecosystems, for the conservation of biodiversity, and for ecosystem management. This paper describes how to analyze it from community composition and associated environmental and spatial data tables.

Methods Beta diversity can be studied by computing diversity indices for each site and testing hypotheses about the factors that may explain the variation among sites. Or, one can carry out a direct analysis of the community composition data table over the study sites, as a function of sets of environmental and spatial variables. These analyses are carried out by the statistical method of partitioning the variation of the diversity indices or the community composition data table with respect to environmental and spatial variables. Variation partitioning is briefly described in this paper.

Important findings Variation partitioning is a method of choice for the interpretation of beta diversity using tables of environmental and spatial variables. Beta diversity is an interesting “currency" for ecologists to compare either different sampling areas, or different ecological communities co-occurring in an area. Partitioning must be based upon unbiased estimates of the variation of the community composition data table that is explained by the various tables of explanatory variables. The adjusted coefficient of determination provides such an unbiased estimate in both multiple regression and canonical redundancy analysis. After partitioning, one can test the significance of the fractions of interest and plot maps of the fitted values corresponding to these fractions.

Weed infestation is a major threat to rice production, and herbicides have been used extensively to control weeds in paddy fields. However, increasing environmental pressures against herbicide use have led farmers to consider alternative approaches to weed control and more emphases have been placed on the development of ecologically sound weed management strategies. Ducks can be used to control weeds, and rice-duck farming systems, which integrate raising ducks into rice cultivation methods, provide an innovative approach to weed management. Field studies were conducted during 2000-2003 in Danyang, Jiangsu Province, to evaluate the long-term influence of rice-duck farming systems on the structure and dynamics of weed communities in paddy fields, including effects on the population density, species richness, species diversity, community evenness and similarity of weed communities across years. The results showed that under long-term rice-duck farming systems, the density of paddy weeds decreased annually and the trend was best fit by the model, y=k+a·e^bx, where the parameter b indicated the rate of decrease of different weed populations. Of the six main weed species in paddy fields, the population density of Fimbristylis miliaceae, Lindernia procumbens, and Ludwigia prostrata decreased rapidly, followed by slower decreases in Monochoria vaginalis, Cyperus difformis, and Echinochloa crusgalli. Rice-duck farming decreased the species richness and species diversity in paddy fields, and increased the evenness of weed communities. Compared to weed communities before the introduction of ducks, Sorensen's similarity indices of weed communities in paddy fields decreased every year, revealing that the structure of weed community was changed substantially. Rice-duck farming provided a more diversified environment for weed growth and seed storage, which greatly limited weed infestation in paddy fields. Consecutive surveys showed that rice-duck farming was an effective control of paddy weeds with more than a 99% overall reduction by the end of the fourth year. Rice-duck farming is an effective and ecologically-based weed management strategy that has significant economic and ecological benefits.

Aims Epiphytic orchids are a major group of epiphytes and vital to maintaining biodiversity and ecosystem functioning in tropical forests. Our objective was to explore diversity and distribution of epiphytic orchids among six different types of old-growth tropical forests (tropical monsoon forest, SF; tropical lowland rain forest, LF; tropical coniferous forest, CF; tropical montane rain forest, MF; tropical mountain evergreen forest, ME; and tropical elfin forest, EF) in Bawangling National Nature Reserve, Hainan Island, China.

Methods We established twelve 0.05 hm² (10 m × 50 m) plots in each type of old-growth forest and recorded species, individuals and position of epiphytic orchids on each tree and liana with diameter at breast height (DBH) ≥ 5 cm in each plot.

Important findings We recorded a total of 9 634 epiphytic orchids belonging to 60 species and 26 genera in the total sample of 3.6 hm². Detrended Correspondence Analysis based on the presence-absence and abundance showed that the epiphytic orchids of the six types of forests were divided into five groups (epiphytic orchids in ME and EF were clustered into one group). There was high similarity between neighboring altitudinal forest types, with the highest value (88.9%) between the ME and EF. Species richness and abundance of epiphytic orchids in the high altitude forest types were greater than in the low altitude forest types, with highest value in the ME. Differences in abundance of epiphytic orchids between in the trunk and the crown were crown > trunk in the SF, LF, CF and MF, no difference in ME and trunk > crown in EF. The ratio of the epiphytic orchids phorophytes to the total investigated plants was higher in the high altitude forest types than in the low altitude forest types. Epiphytic orchid abundance and species richness were both significant positive correlated with phorophyte size (DBH) in each forest type.

In this paper, stamen movement is defined as the movement of stamens with their own energy, either automatically or stimulated by pollinator or other forces, except the forced movement of stamen under the pressure of pollinators. Four main types of stamen movements are classified: stimulated, simultaneous and slow, quick and explosive and cascade. Stimulated movement is normally caused by touching of visiting insects, which can enhance the contact probability of anther/pollen with pollinators or promote contact of anther with self pistil. Simultaneous and slow movement can alter the extent of herkogamy and modify reproductive patterns, and in some plants the stamen can move the anther directly to the self stigma to promote autogamy. Quick and explosive movement can release the pollen rapidly to the air or adhere to visiting insects to promote wind and/or insect dispersal of pollen grains. In cascade movement-in Ruta graveolens (Rutaceae), Tropaeolum majus (Tropaeolaceae), and plants of Loasaceae and Parnassiaceae - the stamens can move one by one and anthers dehisce individually when positioning at the center of flowers. The adaptive significances of cascade movement have not been studied, but, according to ‘pollen presentation theory’, cascade movement can alter the herkogamy and control the pace of pollen presentation and distribute pollen among pollinators by either packaging or dispensing mechanisms, which can greatly enhance pollen removal efficiency. Furthermore, the interferences between stamens and pistil and among individual stamens can be decreased as a result of obvious herkogamy and spatial separation of each stamen caused by cascade movement. In Ruta graveolens, all the stamens move together to the center of flower after the cascade movement, this two-time, multiple-direction stamen movement probably is the most complex stamen movement presently known. Future emphasis in the field of stamen movement should include 1) the effects of stamen movement, especially the cascade movement, on sexual interference and interference among individual stamens, 2) the interaction of stamen movement with dichogamy (temporal separation of male and female funtion) and herkogamy (spatial separation of anthers and stigma), both of which can be modified by stamen movement and 3) the physiology and development of stamen movement.

Aims Our major objective was to reveal the distribution pattern of plant species diversity in the mountainous region of Ili River Valley, Xinjiang, China and explore how environmental gradients influenced the pattern.

Methods Based on a survey of 94 sample plots in the study area, DCCA was performed to analyze the relationships between diversity indices and environmental gradients and GAM was employed to model the response curve of diversity indices to elevation.

Important findings We recorded 259 plant species, including 235 herbaceous species; the species of woody plants were very limited. Communities with complex vertical structure had higher values of diversity. The distribution pattern of species diversity on the northern slope was affected by elevation, slope aspect, slope gradient, total nitrogen, total potassium, soil water content, organic matter, etc., and that on the southern slope was mainly affected by slope gradient, elevation, available phosphorus, soil water content, etc. On the northern slope, Patrick index and Shannon-Wiener index had a bimodal pattern with elevation and Simpson index and Pielou index showed a partially unimodal pattern. On the southern slope all the distribution pattern of species diversity indices showed two peaks, though that of the Patrick index was not obvious. These patterns were formed by the synthetic action of a variety of environmental factors in which elevation played an important role.

Aims Wild soybean (Glycine soja) is commonly accepted as the progenitor species of the cultivated soybean (Giycine max). It contains many characters potentially valuable for supplementing the soybean germplasm pool, yet little research has been done on genetic diversity in natural populations of wild soybean in China. Our objective was to evaluate genetic diversity in natural populations of wild soybean growing in the region of Beijing, China.

Methods We sampled ten representative natural populations in 2005. Every sampled population consisted of 28-30 individuals and was over 10 m apart. Forty public SSR primer pairs over the 20 linkage groups were applied to evaluate genetic diversity.

Important findings A total of 526 alleles (bands) were detected with an average number of 13.15 per locus. Mean expected heterozygosity per locus (H_e) was 0.369 for the populations, and the mean Shannon index (I) for the populations was 0.658. Mean observed heterozygosity per locus (H_o) for the populations was 1.29%. Between-population genetic diversity (H_s) averaged 0.446, and within-population genetic diversity (D_ST) averaged 0.362. Mean coefficient of gene differentiation for loci (G_ST) in the populations was estimated to be 0.544. This study showed that the center-western ecotype had higher genetic diversity than the northern and eastern ecotypes and that there appeared to be ecogeographically genetic divergence in the natural populations between the Taihang and the Yanshan mountains. A strongly drought-tolerant population had very low genetic diversity, and its tolerance gene(s) may be exploited for breeding.

A number of observational, theoretical and experimental studies have indicated that local plant species diversity can have positive effects on ecosystem productivity; however, little is known about the ecological mechanisms that regulate this relationship. To investigate the relationship between plant species diversity and ecosystem productivity and the effect of resource complementarity on productivity, we established experimental communities containing different levels of diversity using nine cultivated annual plant species. To address questions of complementary resource use, we planted each species in monocultures as well as in different polycultures, which allowed us to evaluate complementary effects. Complementarity was assessed by using four analytical methods. The first two methods were tested for an absolute increase in productivity with increasing diversity. The hypothesis was that a polyculture would outperform the most productive monoculture of a component species, defined as overyielding effect 1 (OV₁), and a polyculture would perform better than the average yield of monocultures of the component species, defined as overyielding effect 2 (OV₂). The third method measured the relative yield of the polyculture, Relative Yield Totals (RYTs), and the last method measured the D value, the proportional deviation of the productivity of a polyculture from its expected value. The results indicated that, to a certain extent, species diversity showed a positive effect on community productivity. The relationship between species richness and community productivity could be represented by a quadratic equation y = -98.449x² + 1 039.2x - 42.407 (R² = 0.423). Large differences in productivity were found among treatments with similar levels of diversity indicating that species composition had an important impact on community productivity. Calculation of a complementarity index indicated that about 40% of the polycultures outperformed its most productive component monoculture, more than 95% of the polycultures performed better than the average yield of its component monocultures, and more than 50% of the polycultures had significant RYTs > 1 and D > 0. These results suggest that resource complementarity was partly responsible for the positive effect of species diversity on productivity. Complementarity, however, was not significantly related to species diversity. Four analytic methods were used for estimating the net outcome of complementary effects and the different levels of ecological interaction in a community. Each method had its advantages and disadvantages. Therefore, in assessing how complementarity influences ecosystem productivity, different methods should be integrated.

Tropical montane rain forest (TMRF), one of the primary forest vegetation types in Xishuangbanna, occurs at lower altitude in the north (TMRF I) and higher altitude in the south (TMRF II). In order to understand the plant diversity characteristics of tropical montane rain forests in different zones, six permanent plots (50 m×50 m) of tropical montane rain forest communities at different sites in Xishuangbanna were established, two of which were in the TMRF I and four in the TMRF II. The grid method (10 m×10 m) was used to record all individuals with a DBH greater than 2.0 cm in each plot. Shrub and herb species were investigated in nine 5 m×5 m and 2 m×2 m sub-quadrats, respectively. Plant diversity indices of trees, shrubs, herbs, and three sub-tree layers, and changes in plant diversity indices of communities along the altitudinal gradient were analyzed. The results showed that the total number of plant species in the TMRF communities were 99-181, tree species richness (S) was 54-113, Shannon-Wiener diversity (H′) was 1.648 7-4.049 1, Simpson index (λ) was 0.503 5-0.969 5 and Pielou's evenness index (Jsw) was 0.413 3-0.854 9. For shrubs, S was 35-89, H′ was 2.413 2-3.716 2, λ was 0.762 7-0.958 2, and Jsw was 0.678 8-0.859 3. For the herbs, S was 31-65, H′ was 2.792 1-3.499 2, λ was 0.902 0-0.938 2, and Jsw was 0.729 3-0.838 2. The diversity indices, H′, λ, and Jsw, were greatest in the herb layer followed by shrubs and then trees, whereas species richness showed no obvious differences in the TMRF I. For TMRF II, the species richness and diversity indices, H′ and λ, were greatest in the tree layer followed by the shrub layer and then the herb layer, but the evenness index (Jsw) was not different among the three layers. The species richness, diversity indices and evenness index of the tree layer and shrub layer in TMRF II communities were higher than those in TMRF I communities, most likely due to the superior habitat of the TMRF II communities. Along the altitudinal gradient, all indices (S, H′, λ, Jsw) were greatest at the mid-altitudinal zone (about 1 200-1 220 m) for trees. This can be attributed to the fact that TMRF communities in the mid-altitudinal zone are situated in a ravine area and have the most favorable growing conditions among the six plots. Furthermore, these communities are very near to the seasonal rain forest at lower altitudes, and thus the tropical rain forest plants are very abundant at these altitudes.

Using principal component analysis (PCA) and cluster analysis method, the community structure and species diversity characteristics of corticolous lichen communities in a western Tianshan forest ecosystem were studied in this paper. The results showed that corticolous lichen communities differed with altitude and on different tree types. Based on the results of a multivariate analysis and universal characteristics of habitat, the corticolous lichens communities in the forest ecosystem in western Tianshan can be generalized into four major types: 1) Chaenotheca stemonea + Candellaria aurella Association; 2) Bryoria furcellata + Evernia esorediosa + Physcia tribacoides Association; 3) Parmelia fertilis + Parmelia sulcata + Parmeliopsis ambigua Association; 4) Phaeophyscia ciliata + Phaeophyscia nigricans Association. Community 3 had the highest species diversity (1.920) and community 2 had the lowest (1.562). At the same time, we found that altitude and forest canopy density were the two most important environmental factors influencing the structural patterns of corticolous lichen communities in these forest ecosystems.

Palaeo-biodiversity and environmental characteristics in the Mid- and Late Holocene were investigated in five profiles from Daxigou, Huashuwozi, Xiaoxigou, Dongdaohaizi and Sichanghu, which are located at different elevations and in different vegetation zones on the northern piedmont of Tianshan Mountains, Xinjiang. Selected profiles were located at three vegetation zones. The first was the alpine and subalpine meadow vegetation zone (2 700-3 400 m). Thirty-eight genera and families were identified in the Daxigou profile (3 450 m). Pollen Simpson index was 2.72-7.67 with a mean value of 4.84. The forest-steppe ecotone was from 1 200-1 600 m elevation. Forty-two pollen genera and families were identified in the Huashuwozi profile and 39 in the Xiaoxigou profile at this vegetation zone. The pollen Simpson index of Huashuwozi profile was 4.2-12.4 with a mean value of 7.8, and that of Xiaoxigou profile was 4.13-12.06 with a mean value of 6.89. The last two profiles were located in the typical desert zone (400-600 m). Thirty-two pollen genera and families were identified in Dongdaohaizi profile and 35 in Sichanghu profile. The pollen Simpson index of Dongdaohaizi profile was 1.8 - 18.8 with a mean value of 6.62. The pollen Simpson index of Sichanghu profile was 4.1 - 9.0 with a mean value of 5.55. These results showed that Holocene biodiversity and the pollen Simpson index were the highest in profiles from the desert-steppe vegetation zone.
Our analysis also showed that four periods (3600-3200 aB.P., 1700-1400 aB.P., 1000-600 aB.P., and 450 aB.P.) had the highest pollen Simpson index and highest biodiversity on the northern piedmont of Tianshan Mountains in Xinjiang. Thus, the pollen Simpson index reflects climatic and environmental changes to a certain extent. However, biases exist due to the influence of buried pollen assemblages, low precision in pollen identification - to genera and family levels only, influx of exotic pollen and human disturbances. Pollen that had low representation in the profiles was not taken into account in calculating the biodiversity index, which might underestimate overall palaeo-biodiversity. Due to different abilities of pollen dispersal and transportation, there is high spatial variation in the number of pollen taxa at different sites within the same research district. In addition, sediment composition, strata chronology and human activities have great impacts on pollen preservation, which also affect our ability to estimate palaeo-biodiversity.
All in all, this research showed that the pollen Simpson index is an important index of palaeo-biodiversity and the paleoenvironment,but more research is needed.

Picea asperata is an important tree for the production of pulp wood and timber and a prime reforestation species in western China. P. asperata occurs in the alpine and canyon regions of northwestern Sichuan Province and southeastern Gansu Province (100°-105° E, 30°-35° N), which are important water self-restraint regions. The genetic diversity of ten populations ofP. asperata in the western part of China was assessed using allozyme analysis by horizontal sliceable starch gel electrophoresis. Seventeen loci (27 alleles) of 8 enzyme systems demonstrated relatively low levels (mean H_e=0.096) of genetic variation within populations with values of P_P=29.41% - 41.18%, A_P=1.4 - 1.6 and H_ep=0.06 - 0.131; at the species level, the genetic diversity of P. asperata (P_s=41.18%, A_s=1.2, H_es=0.138) was lower than the mean value of long-lived woody angiosperm species (P_s=59.5%, A_s=2.10, H_es=0.183). Genetic diversity is generally the result of long-term evolution. The low level of genetic variation present in P. asperata populations may be due to severe contractions in the area of distribution and population size during the last glacial period. Wrights F statistics analysis indicated that F_is, a measure of deviation from random mating within the 10 populations, was 0.005 suggesting deviation from Hardy-Weinberg equilibrium and a slight (homozygosity) excess in some populations. The higher level of differentiation (F_st=0.311) among populations than those of other long-lived woody plants may have resulted from factors such as habitat fragmentation, introgression from another species, variation in environmental conditions and differing selection pressure. Low level of gene flow (N_m=0.553 9), low level of inbreeding (mean F_is=0.005), and high level of outbreeding (F_is=0.005) could be caused by environmental deterioration and human disturbance, including over-harvesting. There were significantly negative correlations between Fdh-2-B gene and ecological gradient value (r=0.661 1^*), as well as between expected heterozygosity (H_e) and longitude (r=0.683^*). It was worth noting that the 10 populations harbored the majority of alleles and had higher genetic diversity suggesting that these populations in particular should be conserved in situ and form population used for tree improvement.

Aims Our objective was to reveal the altitudinal pattern of species diversity in woody plant communities of Mountain Helan, which is located on the ecotone between temperate steppe and desert regions in arid northwestern China.

Methods We surveyed forests and shrublands with the quadrat method and used Generalized additive model (GAM) to model relationships between species richness of tree, shrub and herbaceous layers with altitude.

Important findings Altitude accounted for 30%-40% of the variances of species richness patterns, including tree, shrub, herb and total species richness. Both for forest and shrubland communities, 60%-80% of the species were herbaceous and patterns of total species richness with altitude were almost determined by herbaceous species. In forest communities, species richness of the tree layer peaked at middle altitude, because of favorable precipitation and temperature. Species richness of shrub and herbaceous layers in forest communities decreased with altitude, showing a significant influence of forest canopy cover. For shrub communities, species richness of shrub and herb layers also peaked at middle altitude. Aridity at low altitude and cold at high altitude limited species' survival, and only at middle elevations could coexist large numbers of plant species.

Clonal reproduction produces genetically identical ramets. Generally, local clonal diversity is determined by the dynamic balance between loss of established genets and recruitment of new genotypes via sexual reproduction or colonization, as described by Eriksson's recruitment mechanism. However, environmental factors also play important roles in clonal diversity. For example, disturbance will affect local clonal diversity by increased recruitment and mortality of seedlings. Genetic variation is a prerequisite for evolutionary adaptation to environmental changes and plays a key role in the survival of a population or a species. However, recent studies indicate that genotypic diversity also has instantaneous effects. High genotypic diversity might enhance population stability due to high probability of presence of resistant genotypes and/or biological insurance. Recent studies showed that clonal diversity may increase primary production, maintain faunal richness and/or abundance, and affect biogeochemical processes, as does species diversity. Mechanisms of clonal diversity effects on ecosystem functioning are discussed.

Bryophytes on the ground under six types of artificial forests, Picea balfouriana forest (P), Pinus tabulaeformis forest (Y), Pinus armandii forest (H), Larix kaempferi forest (L), Picea balfouriana-Pinus tabulaeformis forest (P-Y) and Pinus tabulaeformis-Pinus armandii forest (Y-H), were investigated in the upper Minjiang River in order to understand the bryophyte composition and synusia structure of these different forest types. In the 19 bryophyte species identified, only 13, 10, 7, 11, 9 and 10 species were present in the P, L, H, Y-H, Y and P-H forests, respectively. Four mosses, Brachythecium glaciale, Thuidium cymbifolium, Entodon concinnus and Eurhynchium savatieri, were common in all six plantations. Another three mosses, Entodon macropodus, Mnium spinosum and Polytrichum formosum, occurred only in the Picea balfouriana forest. The highest frequency of bryophyte occurrence was under the P forest (90%) and the lowest frequency under the H forest (17.65%). Thuidium cymbifolium had the highest frequency (60%) of all species under the P forest, and the second was Brachythecium glaciale (50%). The predominant species, based on the importance value, was Thuidium cymbifolium under the P forest and Brachythecium glaciale, occurred under the other five plantations, which indicated that Brachythecium glaciale was the most common moss species in the study area. In all forests, the P forest had the highest bryophyte diversity (Shannon-Wiener index, species richness index) and the H forest had the lowest diversity. The lowest Simpson index was calculated for the H forest and the highest one for the P forest. The highest similarity index (Sorensen similarity) occurred between the H and Y forests (0.89) and the lowest similarity index between the P and H forests (0.40). The greatest percent coverage (17.79%±1.67%), shoot density ((3 807.11±412.90) shoots•m-2) and thickness ((19.89±1.69) mm) of bryophytes occurred under the P forest, and the lowest values (0.41%±1.49%, (27.99±367.95) shoots•m-2, and (1.80±1.51) mm, respectively) under the H forest. For the Y, L, Y-H and P-H forests, ground bryophyte cover was 5.20%±1.58%, 2.44%±1.58%. 2.73%±1.61%, and 2.71%±1.61%, respectively, shoot density was (623.08±391.71), (566.13±391.71), (253.38±398.41), and (188.69±398.41) shoots•m-2, respectively, and average bryophyte thickness was (9.60±1.61), (14.93±1.61), (9.59±1.63), and (6.69±1.63) mm, respectively. No statistical differences (p<0.05) were found in any of these measures among the Y, L, Y-H and P-H forests. The low bryophyte diversity and limited structure development (density, coverage, thickness) found under all six plantations indicate that, in general, these are poorly developed bryophyte communities. Our results show that the best bryophyte community have developed under the spruce forest with a relatively open canopy and low tree density. Our results suggest that tree thinning or canopy pruning would be an effective measure for improving bryophyte development under dense forests.

The southern fringe of Kumtag Desert is a transition zone for vegetation from rangeland desert type in the Gobi in front of eastern Aerjingshan to wind-accumulation desert type. The diversity of plant species in 20 plots in this area was investigated by calculating the indices of species diversity, richness, evenness and dominance from important values. The results indicated that: 1) The distribution of desert plant community differs with various habitats and landforms. Sympegma regelii community is distributed in the Gobi in front of the mountain; Populus euphratica, Tamarix ramosissima, Glycyrrhiza inflata communities are distributed at the alluvial river course or lowland; Haloxylon ammodendron community is distributed in transitional region from Gobi to desert; and Ephedra przewalskii, Calligonum mongolicum and Haloxylon ammodendron communities are distributed on the sandy mountain with low elevation. 2) The structure and composition of desert plant community are simple, and the species diversity is low. Sympegma regelii community, a rangeland desert vegetation, has the highest Shannon-Winner species diversity indices (1.706); the communities of Haloxylon ammodendron and Ephedra przewalskii, which have obvious feature of desert vegetation, are in the middle in species diversity indices (0.875-0.890); the communities of Calligonum mongolicum, Populus euphratica,Tamarix ramosissima and Glycyrrhiza inflata, characterized by desert forest of which saline desert bushes and saline meadows are scattered in the communities, have lowest value of the species diversity indices (0.079-0.495). 3) The structure of desert plant community is dominated by the bush layer. The species diversity indices of bush layer (0.769-1.451) is much higher than that of herb layer (0.193-0.254), and the diversity in herb layer is strongly influenced by bush layer. 4) The species diversity of desert plant communities shows a gradient of change with respect to longitude, latitude and elevation. For example, rangeland plant Sympegma regelii, with a high level of diversity indices (1.706), is in transition to desert plants Haloxylon ammodendronn community (with a low level of diversity indices of 1.379) in a longitude gradient and to saline Tamarix ramosissima community (with a low level of diversity indices of 0.376) in a latitude gradient. Calligonum mongolicum community, with a low level of species diversity (0.819), is in transition to Ephedra przewalskii (with a low level of diversity indices of 0.890) and Haloxylon ammondendron community (with the diversity indices of 0.645) in an elevational gradient. The transition zone of desert plant communities generally has high level of species diversity and relatively low degree of ecological dominance.

Background and Aims The growing frequency and impact of biological invasions worldwide threaten biodiversity, ecosystem functioning, resource availability, national economies, and human health. Alternanthera philoxeroides is one of the most harmful invasive species and has caused great economic and ecological losses. This species has caused great harm to agriculture, fisheries, as well as to landscapes and native biodiversity, and, at times, has completely overrun and dominated an entire terrestrial ecosystem. It also can form dense tangled mats that float on the water surface of ponds or lakes and shade indigenous aquatic vegetation from sunlight, and thus replace native species. Previous studies have shown that A. philoxeroides can reduce the biodiversity of plants on paddy field ridges, but there have been no other studies on the effects of A. philoxeroides on biodiversity in other habitats. In this study, we conducted a survey of the species and their distributions in different weedy habitats that were invaded by A. philoxeroides in Nanjing during the spring and early summer season in order to interpret the relationship between its occurrence and the environments and elucidate the impact of its invasion on plant diversity.
Methods The abundance, coverage and frequency of each weed population were quantified using the square intercept method in 27 plots. The importance value of each weed was calculated as the sum of the relative abundance, relative coverage and relative frequency. We recorded 142 weed species that belonged to thirty-six families. The data were analysed using principal component analysis (PCA) in SPSS. Thirty-eight out of 142 weed species that had more than 20% frequency occurred in 27 samples were used in the analysis.
Key Results The results showed that the most important factors affecting the occurrence and distribution of weed species were the levels of human disturbance and the soil humidity. According to these two factors, all samples were divided into four groups. Group I included samples collected from experimental fields, and the dominant weed species were Capsella burss-pastoris, Veronica persica and Stellaria media. Group II included samples located in rape farmland which have high soil humidity, and the dominant weed species were Galium aparine var. tenerum, Conyza bonariensis, and Roegneria kamoji. Group III included samples located in public parks or under trees, and the dominant weed species were Vicia sativa, Beckmannia syzigachne, and Geranium carolinianum. The last group was mainly composed of samples distributed on wastelands and waysides which were non-managed or non-irrigated farmland, and the dominant weed species were Erigeron annuus, and Veronica arvensis. The change in the density of Alligator weed and other weeds in the different habitats were analysed. The results showed that the importance value of Alligator weed was high when the soil humidity was relatively high and the intensity of human disturbance was not too great, indicating that Alligator weed has a strong ability to adapt to different habitats. There were different dominants in the different plant communities, which means human disturbance and soil humidity had a key effect on the communities that were composed of a mixture of Alligator and other weeds. When species diversity indices of each group were compared, it was found that although species richness and Simpson's index increased slightly from group I to group IV, but the Shannon-Wiener index and the Pielou evenness index decreased with an increase in the average importance value of Alligator weed.
Conclusions These results indicated that the species composition of the weed community had changed, and the species diversity gradually decreased with increasing dominance of the invasive Alligator weed. These results clearly showed that the invasion of Alligator weed had a negative affect on biodiversity.

The species diversity of a small watershed was investigated following 20 years treatments. Our results showed that the species dominance index of the upper forest canopy layer was higher than other layers and was higher in the artificial forests than that in secondary forests and Liquidambar formosana stands. As a whole, the dominance index for the shrub layer of the 12 communities investigated was small, averaging 0.17. For the herb layer, the dominance index was high in the Ass. Imperata cylindrica var. major community (0.53) and the Ass. Loropetalum chinense-Bromus remotiflorus community (0.51). The species diversity index was high in the canopy layer of the L. formosana forest and natural Pinus massoniana forest but was low in other communities and, in particular, was lowest in the artificial forests. For the canopy layer, the species diversity index was the highest in the L. formosana forest (2.61). A similar trend was found in the subcanopy layers with the highest value found in the P. massoniana + P. elliottii forest. Also, the species diversity index was higher in the artificial forests than that in the secondary forests except for the P. massoniana + Litsea cubeba and Castanea mollissima + L. formosana forests. The richness index was the highest in the shrub layer for all communities and was similarly high in both the canopy and herb layers as the shrub layer in the L. formosana forests. The richness index was higher in secondary forests than that in artificial forests. The evenness index or uniformity index in the herb layer was higher than that in the shrub layer except for the Ass. Ldoropetalum chinense-Bromus remotiflorus and Ass. I. cylindrica var. major stands. For the canopy layer, evenness was as high as 0.76 in the Ass. C. mollissima + L. formosana and Ass. P. massoniana + L. cubeba stands whereas other artificial forests had lower values than that in secondary forests and L. formosana stands. In the shrub layer, evenness was the highest in the artificial forests except for the Castanea + Liquidambar forest. The diversity indices showed large differences between the shrub layer and other communities, and the L. formosana forest showed properties that can be considered atransitionaltype between artificial and secondary forests.

Endophytes, especially asexual and systemic endophytes in grasses, are generally viewed as plant mutualists based on the action of their alkaloids. Enhanced drought tolerance is a well-known benefit of endophytic infection in tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne), and increased tolerance to other environmental stresses like heat, low light and low soil fertility has also been reported. Three endophyte life histories have been recognized: symptomatic of life cycle where the fungus horizontally transmits by meiotic ascospores which induce sterilization of the host, asymptomatic life cycle where the fungus remains internal and there is vertical transmission by plant seeds throughout the season and a mixed mechanism of life cycle, which can be plastic. Neotyphodium endophytes are closely related to sexual Epichloı species, which are the grass choke pathogen, and likely evolved either directly from sexual Epichloı species or by interspecific hybridization of distinct lineages of Epichloı and Neotyphodium. In vertical transmission, only one fungal genotype is transmitted to the seed progeny, which are usually produced by outcrossing in the host. The same fungal genotype is present in seeds that are genetically variable, and the high level of genetic specificity is probably tied to genetic incompatibility constraining the diversity of successful genotype-genotype combinations of the systemic seed-borne endophytes and the host grasses. The defensive mutualism depends on a certain grass-endophyte genotype combination and environmental conditions. Recent studies have suggested that there is a mutualism-parasitism continuum for the symbiosis between asexual endophytes and grasses and that the symbiosis existing in native grass-endophyte symbionts has a more complex mechanism than in agricultural ecosystems. The host-specific endophyte, with negligible biomass, may alter plant community structure, reduce plant diversity and control food-web structure by disrupting the transfer of energy from plants to upper trophic levels. Future studies should focus on how ecology and genetics interact to shift fungal life history traits between the extremes of sexuality and asexuality and antagonism and mutualism. These questions require a more comprehensive understanding of the genetic basis and phenotypic plasticity of traits of the grass-endophyte interactions.

The genetic diversity and genetic variation within and among three natural Carya dabieshanensis populations were studied using RAPD analysis. The result showed that 238 loci were detected by using 20 random primers (10 bp) of which 162 loci were polymorphic (68.1%). Species genetic diversity indicated by Shannon's index was 0.476 1, 58.18% of which was due to within population genetic diversity and 41.82% among population variation. Species gene diversity indicated by Nei's index was 0.314 5, gene diversity within populations (H_S) was 0.186 5, gene diversity among populations (H_ST) was 0.128 0 and the coefficient of gene differentiation (G_ST) among the populations was 0.406 7, 59.33% of which was within populations and 40.67% was among populations. The gene diversity estimated by Nei's index was consistent with that estimated by Shannon's index. These results suggest that there is rich genetic within population variation, which offers excellent prospects for seeding selection. The estimate of gene flow from G_ST (N_m) was 0.730 6, indicating that genetic recombination between populations is quite small, which probably is related to environmental adaptations of C. debieshanensis and population isolation in their high mountain habitat.

Aims Although Caragana davazamcii is an important nitrogen-fixing plant in North China, few studies have focused on its epidermal structure and genetic diversity along a precipitation gradient. Our aims are to determine how changes of epidermal structure of C. davazamcii leaves are related to changes of genetic diversity in different habitats, what role environments play in this relationship, and whether these populations have potential to become adapted to their local environments in different ways.

Methods We established 20 m×20 m plots along the precipitation gradient and randomly collected leaves ofC. davazamcii from natural populations. We studied leaf epidermal structure using a light microscope (LM) and a scanning electron microscope (SEM) and used ISSR-PCR genetic diversity analysis to study differentiation among populations.

Important findings The leaf epidermis of C. davazamcii in different habitats was significantly different as a result of environmental effects. Trichome density, stomatal density, stomatal index and cuticle coarseness increased with changes in average annual rainfall from east to west, as did genetic diversity of populations. Caragana davazamcii showed significant phenotypic plasticity in different habitats, and this may play a critical role in the ecological adaptability of C. davazamcii populations.

The upper reaches of Bailong River, a significant branch of the Yangtze River, is one of the important regions in the Yangtze River Natural Forest Protection Project. Based on the survey and the data from 36 plots, characteristics of species diversity of plant communities in the upper reaches of Bailong River were discussed in this paper. The study showed that richness index varied as follows: tree layershrub layer>tree layer; b) moss-A. fargesii community: tree layer > shrub layer> herb layer; and c) other communities: shrub layer > herb layer> tree layer. Diversity indices in tree layer were lower than that in herb layer and in shrub layer. While the diversity indices between herb layer and shrub layer varied with shade density, i.e. greater the shade density, lower the diversity indices in herb layer. When shade density of stand was about 45%, diversity index in herb layer were almost equal to that in shrub layer; when shade density of stand was about 30%, diversity index in shrub layer were lower than that in herb layer; when shade density of stand was above 55%, diversity indices in shrub layer were higher than that in herb layer. General richness index, evenness indices and species diversity of Pinus tabulaeformis community distributed on the sunny slope were higher than that of the grass-Picea asperata community growing on the shady slope along the same elevation zone (2 500-2 700 m). The study detected that general species diversity and general evenness indices of different plant communities decreased gradually from broadleaf mixed community dominated by Quercus liaotungensis at 2 400 m elevation, to grasses-Picea asperata community at 2 600 m elevation, to bamboo　(Sinarundinaria nitida)-A. fargesii community at 2 800 m elevation, to moss-A. fargesii community at 3 000 m elevation, to R. fastigiatum - A. fargesii community at 3 200 m elevation zone, and then progressively increased in R. fastigiatum shrubs from 3 400 m, with altitudinal increase. The study also indicated that species diversity and evenness index gradually increased from shrubs stage dominated by Spiraea alpina and Sibiraea angustata to broadleaf mixed forest stage dominated by Betula albo-sinensis, to broadleaf and needleleaf mixed forest stage dom inated by B. albo-sinensis and Picea purpurea, and then decreased at the needleleaf community stage dominated by P. purpurea in the natural succession series of P. purpurea community after artificial logging.

Background and Aims Orchidaceae is one of the largest families of flowering plants, and China is one of its most important centers of diversity, with 171 genera and about 1 247 species. Wild species of this family are considered as a key group for plant conservation. Because we cannot preserve all biota in all areas of distribution, conservation priorities must be set and a minimum number of distribution areas needed to preserve the greatest amount of biodiversity possible must be evaluated. Hainan Island is considered as a typical area in China with a high diversity of wild orchids. Previous studies on Hainan Island have focused on investigations of wild orchid resources, but little information is available on their conservation. Analyses of species diversity and endemism patterns provide vital information for conservation planning. Our goal was to determine priority areas with a diverse wild orchid flora and the minimum number of distribution units needed to protect all wild orchid species on Hainan Island.

Methods The 19 administrative counties of Hainan province were treated as the distribution units. Using data on the distribution of the species obtained from the literature and herbarium specimens, we constructed a presence/absence matrix of 202 wild orchids recorded on Hainan Island. Parsimony analysis of endemicity (PAE) was used to identify hotspots of total diversity and endemism at the distribution unit level, and complementarity analyses were applied to show how the target set of species can be conserved with a minimum number of distribution units.

Key Results The database consisted of 1 182 records in the 19 distribution units. Based on this distribution matrix, the analysis generated 424 equally parsimonious trees, from which a strict consensus cladogram was obtained. According to the floristic similarities among the 19 distribution units based on 202 species of wild orchids, two areas were suggested as priorities: one located in southern Hainan Island, represented by Baoting, Sanya, Lingshui and Qiongzhong, and another in the southwest, represented by Changjiang and Ledong. Bootstrap values were 79% and 69%, respectively. Similar results were obtained by parsimony analysis of endemicity. Units with the most floristic similarities of endemisms were Baoting, Lingshui, Ledong, Sanya, Qiongzhong and Changjiang, but the bootstrap values were low, less than 50%. Complementarity analysis showed that at least ten distribution units are required to protect all wild orchid species; listed in descending order of cumulative numbers, they are Baoting, Sanya, Wuzhishan, Lingshui, Baisha, Ledong, Qiongzhong, Dongfang, Changjiang and Qiongshan. Six are needed to protect 30 endemic species: Lingshui, Baoting, Qiongzhong, Ledong, Sanya and Wuzhishan. These six are included in the ten needed to preserve all wild orchid species. The main difference is the hierarchical arrangement of the units. These results indicated that, at least at distribution unit level, the units important to protect all wild orchid species are also important to preserve the endemic species.

Conclusions An assumption of both parsimony and complementarity analyses is complete knowledge of the distribution of each species in a region, but this is unlikely for wild orchids on Hainan Island. Another problem with our study is that we chose the administrative counties of Hainan Island as the distribution units rather than units based on biogeographic criteria. Despite these limitations, our study provided a baseline set of protected areas for the conservation of wild orchid diversity on Hainan Island that can be supplemented to meet other conservation and socio-economic needs and objectives.

Aims Larch forests are important for timber harvesting and water-soil conservation in North China. To explore the distribution, community structure and species diversity of larch forests is important for the vegetation conservation and sustainable utilization in North China.
Methods We collected species composition and local environment for 215 forest plots dominated by three common larch species, namely, Larix principis-rupprechtii, L. kaempferi and L. chinensis, in North China during 2000-2017. Among these types, L. kaempferi forests are planted, while L. chinensis forests are almost natural, and most of L. principis-rupprechtii forests are natural. Based these data, we used the canonical correspondence analysis (CCA) to explore the relationship between species composition and environment. We also explored the pattern of community structure and species diversity of these three forests in relation to environmental factors.
Important findings Mean annual air temperature (MAT) was the most important factor for the distribution of these larch forests. The proportion of natural forest decreased, while that of planted forest increased, with MAT. Diameter at breast height (DBH) and height distribution of three larch forests were right-skewed, indicating that all of these larch forests are at relatively stable successional stage. Species richness differ remarkably among different larch forests, which was highest in the L. chinensis forests (39.3 ± 17.9), followed by the L. kaempferi forests (37.4 ± 22.4), and lowest in the L. principis-rupprechtii forests (planted forests 27.2 ± 17.7, natural forests 27.5 ± 13.8). Species richness, the maximum DBH and the maximum height decreased with latitudes and longitudes. Species richness, the maximum DBH and the maximum height increased with annual precipitation. However, species richness showed no significant trend, and the maximum height increased, while the maximum DBH decreased, with MAT. The patterns of species richness along geographical and climatic gradients were consistent between the planted, the natural and the overall (including both planted and natural) larch forests. However, the patterns of community structure differed remarkably among planted, natural and overall larch forests. The maximum height of planted forests increased, while that of natural forests decreased, with latitude and longitude. The maximum DBH and height of natural forests decreased, while those of planted forests increased, with MAT and annual precipitation, respectively.

Three fragments of tropical rainforest in Xishuangbanna, southern Yunnan and within the Lower-Lancang/Upper-Mekong River basin, were sampled to investigate species diversity patterns based on comparisons with a contiguous tropical rainforest. Compared with the contiguous forest, the fragments were lower in plant abundance, species diversity indicies, a lower percentage of mega-phaenerophytes, meso-phaenerophytes, chamaephytes and epiphytes, but had a higher percentage of liana, micro-phaenerophytes and mini-phaenerophytes. The floristic composition was also different in the fragments with a greater percentage of pan-tropical and tropical Asia to tropical Africa elements increased, whereas the percentage of regional or local elements decreased. Meanwhile, tree species in the upper canopy layer were more stable than that in the lower layers of the fragmented forest. The animal species diversity and evenness were higher in the contiguous forest than in the fragmented forests, which apparently were due to better habitat size and quality. The relationship between changes in the microclimate of the forest fragments and species changes were also considered. The interior forest of the fragmented forests transformed from a wet-cool to dry-warm microclimate, called the internal effect, and was found to be an important mechanisms accounted for observed species changes.

Understanding the relationship between biodiversity and ecosystem function is central to the Global Change and Terrestrial Ecosystem (GCTE) project as well as to ecosystem ecology in general. Productivity and nutrient maintenance, both critical ecosystem functions, can be measured in relation to species diversity to test how ecosystem functions are affected by species diversity. We studied changes in species diversity and productivity along elevational gradients in alpine meadow grasslands to assess the influence of changing species diversity on productivity.The results show a significant unimodal pattern of species diversity across the elevation gradient with species diversity highest at mid-elevations. Maximum species diversity occurred at intermediate levels of productivity and species richness. Above-ground biomass decreased with increasing elevation and below-ground biomass was greatest at low and high elevations and lowest at mid-elevations. Below-ground biomass varied during the growing season and vertically within the soil profile: maximum underground biomass occurred at the beginning and end of plant growing and was distributed primarily in the top 0-10 cm of soil.

Aims The objectives were to compare the fine root biomass, necromass and their distributions in the soil profile and examine the effects of plant species diversity on the morphological properties of live fine roots at different soil depths among four forests along a gradient of increasing plant species richness in subtropical southern China.

Methods The fine root samples were collected in March 2010 in four forests: coniferous monoculture (Cunninghamia lanceolata), coniferous pioneer species (Pinus massoniana-Lithocarpus glaber), deciduous (Choerospondias axillaris) and evergreen broadleaved (Cyclobalanopsis glauca-Lithocarpus glaber). In each forest, three soil cores containing fine roots were taken at each of three soil depth (0-10, 10-20 and 20-30 cm) at each of upper, middle and lower slope positions. Living and dead roots were manually separated and then oven dried at 75 °C to constant mass to determine weight. Living roots were scanned with a Win-RHIZO 2005C to measure morphological parameters, including total root length, total root volume, number of root tips and forks.

Important findings Fine root biomass tended to increase along the gradient from the plantation to evergreen broadleaved forest. Total fine root biomass within the 0-30 cm soil depth differed significantly among the forests, but there were no significant differences in living root biomass. Fine root biomass density decreased exponentially with soil depth at similar rates among the forests. With exception of the plantation, fine root biomass showed clear differences in their distribution in the soil layers, indicating significant belowground spatial niche segregation of the vertical root distribution patterns in the more species-rich stands. Differences in root biomass did not lead to significant differences in fine root morphology on a stand area basis.

Over the recent decade, biodiversity and ecosystem multifunctionality (BEMF) has aroused as an emerging reserach hotspot in the filed of biodiversity and ecosystem functioning. Ecosystem multifunctionality is defined as the capacity of an ecosystem to provide multiple ecosystem functions simulateneously, it has received broad consideration by community and ecosystem ecologists. In this study, we first conducted a literature review of the research history in biodiversity and ecosystem multifunctionality. Next, we summarized the major trends in biodiversity and ecosystem multifunctionality research including the impacts of biodiversity dimensions, global change drivers and spatial-temporal scales on ecosystem multifunctionality. We reviewed the new research methods and research directions emerged in the field. We also defined a new concept, i.e., ecosystem multiserviceability (EMS) based on the distinction between ecosystem functions and ecosystem services. Finally, we briefly summarized the limitations in current research of biodiversity and ecosystem multifunctionality/multiserviceability (BEMF/BEMS) and presented the outlook for future study.

Aims The alpine meadow degradation could have profound effects on the grassland productivity. The aim of our study is to clarify the dynamic response of community productivity and species diversity in the process of alpine meadow degradation.

Methods In the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Northern Tibetan Grassland Ecosystem Research Station (Nagqu station), we conducted stages experiments with multiple degradation levels: control, mild degraded meadow, moderate degraded meadow, severe degraded meadow and serious sandy meadow.

Important findings The response of aboveground biomass to alpine meadow degradation showed a linear or nonlinear increased response patterns, but the belowground biomass and total biomass decreased nonlinearly. As observed in measurement of aboveground biomass, Margalef index, Simpson index, Shannon-Wiener index and Pielou evenness index also exhibit a nonlinear increased response to degradation. The results of structural equation models showed that belowground biomass has a positive relationship with soil carbon content (p < 0.05) and volume water content (p < 0.1). However, soil nutrient and soil physical properties had no significant impact on aboveground biomass (p < 0.1). Compared with soil physical properties, soil nutrition is an important factor influencing the diversity index. In our study, the nonlinear responses of productivity and diversity of alpine meadow were described by using the multiple levels of degradation in space. The results suggested that aboveground productivity cannot interpret the degree of degradation of alpine meadow, and by contrast, alpine meadow degradation should be measured by the change of plant functional groups, such as edible grasses and poisonous forbs.

Background and Aims The fungal endophytes in grasses grow intercellularly and systemically in aboveground plant tissues. Vertically transmitted asexual endophytes (Neotyphodium) forming asymptomatic infections of cool-season grasses have been repeatedly derived from sexual species (Epichloı) that abort host inflorescences. The phylogenetic distribution of seed-transmitted endophytes is strongly suggestive of cocladogenesis with their hosts. Endophytes are considered plant mutualists: they receive nutrition and protection from the host plant while the host plant may benefit from enhanced competitive abilities and increased resistance to herbivores, pathogens, and various abiotic stresses. Most studies of grass-endophyte associations have been undertaken with two economically important plant species, Lolium perenne and Festuca arundinacea. The interactions between endophytes and other grasses in natural plant communities, however, are seldom concerned. Much less attention has been paid to native grasses in Inner Mongolia Steppe, which lies in the north of China and is an important part of Steppe in Eurasia, and only limited published symbiosis studies are available in this natural ecosystem. Thereby, a more comprehensive view of the ecology, diversity of endophytes and their interactions with host plants becomes essential.
Methods Our research of grass (Achnatherum sibiricum) associated with Neotyphodium endophyte (a new grass-endophyte association) was carried out in the Inner Mongolia Steppe, China. Twenty-seven endophyte strains were isolated from four A. sibiricum populations including Hulingol (H), Xi Ujimqin Qi (X), Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences (IMGERS-CAS) (I), and the Leymus chinensis plot of the IMGERS-CAS (L), respectively. Colony morphology, growth rate on potato dextrose agar (PDA) and conidial measurements of isolates were used to characterize diversity of endophytes hosted by A. sibiricum. The genetic polymorphisms of Neotyphodium species from the four A. sibiricum populations were also analyzed using random amplified polymorphic DNA (RAPD) markers.
Key Results Four morphological groups of Neotyphodium species and five individual morphological types were described based on the colony morphology, growth rate, and conidial shape and size. A total of 463 bands were obtained using 20 RAPD primers, of which 461 bands were polymorphic. A total of 93 unique loci were obtained, accounting for 20.1% of the total amplified loci. Nei's diversity index (h) and Shannon's diversity index (I) were 0.238 and 0.387, respectively. In the four populations (H , X , I, and L), the value of h was 0.122 0, 0.180 4, 0.146 3 and 0.210 7, respectively. The four populations may be ranked in a descending order as L > X > I > H, and the I of the four populations had a similar trend. The fixation index (F_ST), the coefficient of gene differentiation (G_ST), and the genetic differentiation (Hsp-Hpop)/Hsp (estimated by Shannon's diversity index) were 0.205 1, 0.300 4, and 0.355 0, respectively. The genetic variation of Neotyphodium species mainly existed within populations. Genetic similarities within each population were found to be in the range of 0.647 9-0.943 8 in similarity, and the average genetic distance among the four populations was 0.285 8, varying from 0.057 8 to 0.433 9. Clustering analysis based on Nei's unbiased genetic distance and UPGMA method showed that there were seven distinct RAPD genetic groups.
Conclusions The high incidence of endophytic infection in A. sibiricum was indicative that the presence of the endophyte gave the grass a competitive advantage over non-infected grasses. The study also indicated that there were higher genetic diversity based on morphological and RAPD results, and that there were relatively high genetic variations among the four populations and higher genetic differentiation of Neotyphodium sp. within a geographical region. Most of the genetic groups were related to geographical origins of the strains. The dendrogram of genetic distance matched rather well with the morphological data, as reflected by the four morphotypes.

Aims Juglans regia and J. sigillata are important economic nut trees and are widespread in Sichuan Province. Accurate evaluation of genetic diversity and relationships between species is essential for effective preservation of germplasm resources and breeding. Traditional methods for assessment of genetic diversity in walnut, based on morphological, physiological and biochemical studies such as isozyme analysis or RAPD makers, are sensitive to environment so results are not reliable. AFLP has been applied extensively and effectively in population molecular ecology research and population genetic studies. Our aims were to identify genetic structure among populations and to examine genetic relationships between the two species.

Methods We compared three wild J. regiapopulations occurring at Qingba Mountain, Daduhe Valley, and southern Ganzhi District in Sichuan Province, and one wild J. sigillatapopulation at Panzhihua District in southeastern Sichuan Province. We selected 46 samples to analyze by AFLP molecular maker technology using 4 pairs of primer combinations screened.

Important findings We obtained 244 bands including 146 polymorphic bands. The percentage of polymorphic bands (P) was 59.84%. For the J. sigillatapopulation, percentage of polymorphic bands (P) was 52.05%, effective number of alleles per locus (A_e) was 1.339 9, and Nei’s gene diversity index (H) was 0.196 1, Shannon’s information index (I) was 0.289 8. For J. regiapopulations at species level, estimates were P=55.33%, A_e=1.322 9, H=0.190 8, andI=0.286 3. Although these findings showed that genetic diversity of J. sigillatawas slightly higher than the other species, genetic diversity level was generally equivalent. Shannon information index, Nei’s genetic diversity coefficient and analysis of molecular variance showed that 85.64%, 87.4%, 88.93% genetic diversities, respectively, distributed within populations at the species level. Most variation (80.65%) consistently originated from the interior of groups. The population ofJ. sigillatapossessed the greatest amount of unique bands, accounting for 4.5% of the total amplified bands, which indicated genetic variation between two species. The genetic differentiation coefficient (G_st=0.093 5) between two species is very low. Juglans regiashowed high genetic affinity to J. sigillata.Nei’s Genetic distances between populations varied from 0.038 2 to 0.069 2 and genetic similarities ranged from 0.933 2 to 0.962 5, which indicated there were high similarities among populations. UPGMA analysis revealed that threeJ. regiapopulations clustered first, and genetic distance was closest between the Daduhe Valley and southern Ganzhi District populations.

Aims Our objective was to determine 1) the phenotypic variation of cone and seed in natural populations and 2) the relationship between phenotypic variation of natural population and different distribution areas in Picea crassifolia.
Methods Field investigation and analysis of the natural distribution of P. crassifolia in Qilian Mountain led to our selection of four cone characters and four seed traits in 10 trees from each of 10 populations. We examined morphological diversity among/within populations based on analysis of eight phenotypic traits. Variance analysis, multi-comparison, correlation analysis and hierarchical cluster analysis were used to analyze experimental results.
Important finding Analysis of variance for all traits showed significant differences among/within populations except for cone dry weight and cone length/cone width. The mean phenotypic differentiation coefficient (Vst) among populations was 27.18%, compared to 72.82% within populations. In different individuals within populations, the CV of cone length, cone width, cone dry weight, cone length/cone width, seed length, seed width, seed length/seed width, 1 000 seeds weight was 10.08%, 5.80%, 19.29%, 9.66%, 8.38%, 15.34%, 6.52% and 13.94%, respectively. Most of the cone and seed traits were positively correlated. The cone dry weight, seed length, 1 000 seeds weight, cone length, cone width were thought to be the most important cone and seed traits that were easy to measured in P. crassifolia. The spatial variation of traits of natural populations was related most strongly to longitude. According to UPGMA cluster analysis, the 10 populations of P. crassifolia could be divided into four groups. This study indicates that there is rich phenotypic variation of cone and seed in natural populations of P. crassifolia in Qilian Mountain and thereby provides theoretical references and basic data for genetic resources conservation, utilization and improvement in P. crassifolia.

Aims Island forest is a major vegetation type of the Sanjiang Plain in northeastern China. However, its species diversity is at risk of decline. Our objectives were to 1) describe the flora, 2) determine the level of plant diversity, and 3) determine relationships between diversity indices and patch characteristics (area, perimeter and shape index).

Methods We used Quick Bird satellite image data to identify a 65 km² study site. The quadrat method was used to investigate community patch characteristics such as area, perimeter and shape index, which were analyzed with Erdas Imagine 8.7. Four indices were selected to describe plant diversity: richness (R), Simpson (D), Shannon-Wiener (H'), and Pielou (J_sw).

Important findings The 19 patches of the island forest had 140 species of vascular plants of 44 families and 102 genera dominated by cosmopolitan and temperate genera. Our data suggested that, compared with the neighboring community in the Honghe Nature Reserve, some plant species had disappeared. The diversity indices were significantly different among shrub layers of the Populus davidiana, Betula platyphylla and P. davidiana + B. platyphylla communities (p<0.05). Additionally,R, D and H' indices of different layers were as follows: herb layer > shrub layer > tree layer, with significant differences among them ( p<0.01). While statistically significant correlations were observed between theR index and patch area (r=0.591, p<0.01), perimeter (r=0.674, p<0.01) and shape index (r=0.584, p<0.01), no correlations were noted for theD, H' and J_sw indices. Diversity levels remained relatively high after human disturbance. The greatest difference among patches was noted in herb layers. Our data also suggested that gap disturbance was an important cause of higher understory diversity. Plant species richness increased with patch area, perimeter and shape index, most likely resulting from edge effects. Our results demonstrated that the island forest plays an important role in preserving plant diversity in the region.

Aims Polygonum viviparum, which is widely distributed in eastern Qinghai-Tibet Plateau in China, is a clonal plant species with two modes of reproduction, clonal propagation by below-ground rhizomes and bulbils and sexual by seeds. This study investigated clonal structure and diversity (monoclonal or multiclonal population) and the relationship between clonal diversity and the altitude. Our objective was to examine the adaptive strategy of alpine plants to varied environments and establish a foundation for understanding reproduction and distribution of clonal plants.
Methods We selected seven populations in eastern Qinghai-Tibet Plateau along an altitudinal gradient and sampled 20 individuals in each population with at least 1 m between individuals to avoid individuals from the same clone. We employed random amplified polymorphic DNA (RAPD) technology for studying clonal structure and diversity and analyzed the relationship between clonal diversity and altitude by SPSS software.
Important findings We selected 13 random primers for amplification and found 117 repetitive loci with 84 polymorphic loci (total average percentage of polymorphic loci was 71.79%). We differentiated 43 RAPD genotypes among the 140 plants sampled. Mean Simpson's index was 0.639, and mean PD was 0.307, slightly higher than the mean of Ellstrand (PD=0.17, D=0.62). There was a clear mosaic among P. viviparum clones, probably because of diverse clonal structure. The formations of P. viviparum populations included guerilla, phalanx and a transitional type. Clonal diversity was independent of altitude.

Biological invasions are a pervasive environmental problem and are an important focus of ecological research and environmental management. Research on the function of biodiversity has stimulated an interest in the mechanisms underlying the invasibility of plant communities. Although many theoretical and observational studies suggest that diverse communities are more resistant to invasion by exotic species than less diverse communities, results of experimental studies are not conclusive and this remains a highly debated topic.

In this experiment, a series of manipulated grassland communities with different levels of species diversity and different species functional groups (16 species belong to C3 grasses, C4 plants, forbs and legume respectively) were established to test Elton's diversity-invasibility hypothesis by studying the pattern and process of invasion by Alternanthera philoxeroides. Total biomass of the invasive species, an index of community invasibility, was recorded in each community type. Our results showed that in communities with higher functional group diversity, the biomass of A. philoxeroides was significantly lower due to decreased niche opportunity whereas species diversity alone did not show any significant effects on the biomass of the invasive species. The results showed that community invasibility was negatively correlated with functional group diversity suggesting that the diversity of characteristics of species rather than species diversity itself was important. Niche opportunity for invasive species in communities might be a key determinant influencing its invasibility. The characteristics of functional groups also influenced the success of the invasion. Annual grasses with short life spans and nitrogen-fixing legumes were more susceptible to invasion. Moreover, A． sessilis, which belongs to the same morphological and functional group as A． philoxeroides, caused a significant decrease in establishment of the invader species. This suggests that competition might be more intense within functional groups than across functional groups. Because community invasibility is influenced by many factors and their interactions, the pattern and mechanisms of community invasibility are likely to be more complicated than we have acknowledged so far. More experimental work coupled with theoretical modeling studies are needed to better understand the characteristics of community invasibility.

Aims Our objective was to examine population genetic diversity and species divergence of two pine species (Pinus massoniana and P. hwangshanensis) with overlapping distributions in southeastern China.

Methods We estimated levels of nucleotide diversity and an analysis of molecular variance (AMOVA) of the two species based on sequence data of two nuclear loci for 88 individuals from 22 populations of the two species across most of their range of distribution. Gene genealogies of each locus were constructed by coalescent simulations using the Median-Joining model.

Important findings Both species exhibit low levels of nucleotide diversity at two nucleotide loci, and the level of silent nucleotide diversity is two times higher in P. hwangshanensis (π_sil = 0.003 40) than that in P. massoniana (π_sil = 0.001 71). The population differentiation (F_ST) is also significantly different between the two species (P. massoniana, 0.059; P. hwangshanensis, 0.339, p < 0.05). These genetic differences in the population structure of the two species may result from their differences in distribution and habitat preference. Hierarchical AMOVA revealed that the average of variance components between species is 48.86% based on the two loci and is significantly higher at locus GI (77.24%) than locus C3H (20.48%). In addition, shared haplotypes were only observed in C3H rather than GI. Thus we speculate that GI (control of flowering time) may have experienced speciation-related selection, which further accelerated its lineage-sorting divergence between the species.

Clearcutting, a commonly used forest management practice in eastern Qinghai-Tibetan Plateau, is a major driving force for land use change resulted in the drastic degradation of subalpine forest ecosystems. One of the most serious consequences is causing d

The Helan Mountains (38°10′－39°30′　N and 105°45′－106°45′　E) is situated on the eastern edge of the Alashan Plateau and the western edge of the Yinchuan Plain and extend about 270 km from north to south and about 20－40 km east to west. Its general altitude ranges from 2 000 m to 3 000 m with the highest summit at 3 556 m above sea level and relative elevations are 1 500－2 000 m. The Helan Mountains form an important boundary of climate and vegetation in northwest China: the eastern side of the Helan Mountains belongs to steppe climate and steppe vegetation and desert climate and desert vegetation characterize the west resulting in two different biomes. The mountains are a core area of the Alashan-Ordos biodiversity center that is among the top eight centers of biodiversity in China. It is a rich source of plants for the arid west and is an important pivotal point that connects the floras of the Qinghai-Xizang Plateau, the Mongolian Plateau and North China. Hence, it is very important to study the biodiversity of the Helan Mountains. The diversity and spatial distributional characteristics of plant communities are discussed in this paper. Based on our observations and research over many years, we have classified 11 vegetation types, and 55 formations in the Helan Mountains. The vertical zonation of the vegetation is strongly developed: vegetation belts can be divided into the desert belt (below 1 600 m asl), the steppe belt (1 600-1 900 m asl), the coniferous forest belt (1 900-3 100 m asl), and the alpine shrub or alpine meadow belt in the alpine or sub-alpine zone (>3 100 m asl). There also is a strong differentiation of vegetation on sunny and shady slopes. In the steppe belt of low hillsides, steppe communities inhabit sunny slopes but mesophilous shrub occur on shaded slopes. In the coniferous forest belt in the mid-elevation zone, the community of Picea crassifolia is distributed widely on shaded slopes but open forests of Ulmus glaucescens and Juniperus rigida or other mesophilous shrub occur on the sunny slopes. At 3 000 m and upwards, the vegetation of sunny and shade slopes is similar. The vegetation also is differentiated in an east-west and north-south direction resulting in some unique communities. The climate is warm and dry on the east side of the Helan Mountains and some thermophilic plants such as Zizyphus jujuba var. spinosa and Ostryopsis davidiana are distributed on the eastern side only. On the western side, the climate is cool and wet and there is a greater proportion of forests. The mid-elevation zone is the main body of the Helan Mountains, and the vegetation comprised primarily of forests and mesophilous shrub. The degree of desertification is very distinct in both the north and south segments of the mountains, but the communities are different. In the north, Ammopiptanthus mongolicus, Salsola laricifolia and Tetraena mongolica are dominant whereas Ephedra rhytidosperma, Syringa pinnatifolia var. alashanensis are dominant in the south. Furthermore, there are four endemic communities with Syringa pinnatifolia var. alashanensis, Ephedra rhytidosperma, Leptodermis ordosica and Hippolytia alashanensis in the Helan Mountains.